Heat Shrink Sleeve Quality Concerns

Heat Shrink Sleeve Inspection Concerns

NOTE:  This is not a product I sell or represent.

     I was contacted this weekend by a customer located somewhere outside of the USA.  They have been installing a heat shrink sleeve system purchased and manufactured in the far east.  Having installed a number of shrink sleeves already, they are finding a number of different things to be highly concerned about.  They asked my opinion:  are their concerns about the heat shrink sleeve issues they are observing valid? 

     I will get into more detail, but the quick answer is:  YES.  This person I'm speaking with is very observant and quite smart.  They are absolutely correct to be concerned about these issues. 

     I shared with them that most every specification that crosses my desk over the course of the last couple of years has a very strict direction in terms of heat shrink sleeve manufacturers:  "No shrink sleeve manufactures from China, Korea or India will be accepted."  This is not my recommendation - this is a policy that I see listed in specifications over and over.  Why is it specified like that?  My guess is that most companies are requiring manufacturers other than those countries because they have tried or evaluated shrink sleeve material from China/Korea/India in the past and they quite simply haven't found the products quality to be at an acceptable level yet. 

     That makes perfect sense to me.  I have evaluated products from those countries a number of times over the years.  They are always looking to break into the US market - and it is very common for me to be offered samples on just about a monthly basis.  I always see the same things when I accept their offers:  adhesives that don't flow or bond well -- and backing that is made from a low density PE and doesn't bring much to the table in the way of strength.  That is a very bad combination!  A shrink sleeve that doesn't stick well -- is not going to protect your pipeline!

     So back to this particular case.  This is a high temp line (80C) and upon inspection after installation - some red flags were raised:

     Here we see some spaces where, upon shrinking of the sleeve, as the sleeve (naturally) begins to longitudinally shrink, the backing pulls back leaving some gaps in the adhesive.  These are areas that might be seen as 'fish eyes' in the two part epoxy world.  In these cases, the backing pulled back and the adhesive had flowed out -- but for some reason, these holes were left behind (there is another lower in the pipe that can be seen). 

     Now, this is does indeed raise a lot of issues - and we are not going to be able to answer them here.  First of all - it is possible this could be an installer issue.  It could be that the PE jacket here wasn't properly cleaned and that what happened there was that dust or dirt was on that little piece of PE and as a result, the adhesive didn't bond to the PE.  That is certainly possible.  It could also be though that this particular adhesive simply isn't flowing very well - and isn't filling properly underneath the sleeve.  If there are gaps here -- what is the step down area going to look like?  What is the weld bead area going to look like?  We can't know - but it could certainly be worth evaluating. 

     Of the 2/3 issues we will look at here - this one might be the most innocuous.  We can't definitively say what is going on - we can't say with 100% confidence that the adhesive has failed here - but we can certainly say 'this is something we would like to look more deeply into'.

     Onto the other issues here (I'll show two photos):

     Here we have two photos / areas that are showing the same problem:  hair line cracking of the adhesive.  This is HIGHLY concerning.  In the bottom picture, those cracks are what I would consider to be:  significant.  I know the top picture is more difficult to see - but those also are very concerning.  My first guess is that these adhesive are just not flexible enough to be used as a pipe coating.  If we see cracks here, where there has really been minimal stress on the pipe - I quite honestly can't imagine the sleeve offering any quality corrosion prevention after even a few weeks of normal and natural pipe movements.  We can clearly see (in the cracks) the beginnings of a leak path.  For all we can tell, the adhesive is also cracked underneath the back.  Not good.  Not good at all. 

     In recent years, there have been a number of shrink sleeve manufacturers pop up.  It isn't difficult to find some cheap labor - and a chemist or two to teach about peroxide bonding.  In addition, in some parts of the world, they try to reverse engineer different adhesives and mastics (this is not a simple task) and quite frankly, they think they copy them well...but they do not.  They then sell a cheap and inexpensive product into different marketplaces around the world (focusing specifically on the Middle East, Africa and Eastern Europe) and they dump a bunch of zero quality pipeline coatings on these jobs. 

     They pitch that they will save you money --- but your pipe is not corrosion protected.  They cost you money.  They cost you lots of money.  It may be a few years but you will have massive corrosion problems and when they are discovered, that Chinese shrink sleeve manufacturer will have changed their name, or gone out of business -- or it will turn out that you were actually dealing with a broker, not a manufacturer - and so the manufacturer is unwilling to stand behind their product because it was the brokers fault (these are all things that I've heard).  

     Raychem (now called Covalence / Seal for Life) - took decades, many PHD's, many chemists -- to perfect that design, creation and consistent manufacture of specialized adhesives and mastics.  Those cannot be reverse engineered.  They can not be copied over the course of a couple of years.  Please do not support the pretenders -- please specify and use only proven products with long successful use histories. 

Backing Material Properties of Heat Shrink Sleeves

Backing Material Properties of Covalence Shrink Sleeves (formerly Raychem shrink sleeves)

     When attempting to determine physical properties of the backing of heat shrinkable sleeves, it is incredibly important that you are aware of the fact that different manufacturers products will exhibit dramatically different qualities.  

     This is incredibly overly simplified and any true in depth analysis would require a much more thoroughly educated communicator.  But for the purpose of this specific discussion, I am going to break backing types down into two different categories:  High Density and Co-Polymer heat shrinkable backings. 

      Aside from heat shrinkable backing construction / chemical make up; it is also important that any potential user or specifier of heat shrinkable sleeves understand that there are also two commonly used crosslinking methods out in the world today; radiation crosslinking and chemical crosslinking.  

     In recent months I've seen more and more field joint coating specifications coming across my computer that specifically say:  products from India or China will not be accepted.  One of the (many) reasons for this is that chemical crosslinking is very often the crosslinking method of choice in those countries.  Why is that?  Thanks for asking - that is because chemically crosslinking is dramatically less expensive than radiation crosslinking is.  Less expensive cross linking method (plus lower quality backing, lower quality adhesives and lower cost labor) leads directly down the path to 'lower quality product.'  And after a few field problems and coating failures -- the path generally leads to a "I will not accept _______" clause on coating specifications and RFQ's.  

     So, what advantages is a high density backing going to have over a co-polymer backing?  What advantage is a radiation crosslinked backing going to have over a chemically crosslinked backing?  Interestingly, the differences strengths and weaknesses are going to be pretty similar in both cases, so using a low cost co-polymer backing with a chemically crosslinked backing is going to act like a double whammy (a double whammy isn't good).

     By being selective about the backing construction and cross linking method you are essentially getting a product with better: penetration resistance, cut through, abrasion resistance, tensile strength, Shore D hardness, shrink force, heat/flame resistnace and impact resistance.  Let's look just a tiny bit closer at those characteristics below:

     Penetration resistance:  how well does the material withstand attempt to penetrate it?  That pretty much sums it up.  How does this come up in a practical sense?  During backfill, there is a chance that this could come into play.  It would also come into play in a case where the pipeline is resting on something (sharp-ish).  The weight of the pipeline, plus the dirt, would be squeezing the coating between a rock and a hard place (so to speak) and penetration resistance can become an incredibly important characteristic.

     Cut through:  similar to penetration resistance, but picture a 'gash' instead of a hole being poked in the coating.  This could happen when the line is being lowered into the ditch, or it could happen during a road bore or directional drill, or it could happen due to normal pipe movements through out the life the pipeline (picture the coating being forced to 'slide along' a sharp-ish edge due to one of the forces listed there).

     Abrasion resistance:  How does the backing hold up to normal back and forth pipe movements along the soil, rocks, roots, whatever?  Over the course of months or years, is the backing thickness of the sleeve going to be worn away by this movement?  Will you eventually end up with a backing that is only 10 mils thick?  How about if your line will be involved in a 2000 foot road bore?  Is that going to compromise your coating?  Good abrasion resistance is important, don't let anyone fool you.

     Tensile strength:  how much force does the backing take before it breaks/splits?  This is a little like cut through and penetration resistance, but instead picture a tremendous amount of weight putting only one small section of the coating into sheer.  How much force will it take before the coating gives?  

     Shrink Force:  how much force is involved as the backing shrinks down to the pipe?  This is amazingly important.  Did you know that when considering the true purpose of a shrink sleeve, you have two components:  backing and adhesive.  The backing has two functions:  1) as a vehicle to get the adhesive onto the pipe and 2) to physically protect that adhesive for the life of the line.  As a shrink sleeve is installed, the adhesive flows and fills....thanks to the force of the shrinking backing exerting force on the adhesive and assuring that it fills every little area.  Without the proper shrink force, your adhesive is likely to be inconsistently distributed.  That isn't good.  You do not want an inconsistently distributed adhesive on your pipeline underneath your backing.

     I'll stop there for now.  But let me just sum up by saying that choosing which shrink sleeve manufacturer you use is incredibly important.  There are a ton of different methods for some folks out there to reduce their costs by modifying their products in a way that is likely not going to be obvious...until they've been installed and buried for a few months.  Sure, you will likely be on to the next project; but ultimately, someone is going to have to answer for those decisions to compromise coating quality in order to save a few pennies.